The present invention relates to the field of timing circuits and methods of operation of timing systems. In one embodiment the invention provides an improved method and device for generation of appropriate control signals for dispensing cleaning materials and other materials into warewashing machines.
Warewashing machines are well known to those of skill in the art and widely used in a variety of industries. Most commonly such devices take the form of commercial dishwashing machines and the like. Among warewashing machines, door loading and conveyor type machines are most common. Door loading machines operate on a "batch" basis in which articles are loaded into the machine, the articles are placed through various cycles such as wash, rinse, and the like, and the articles are removed. In conveyor type machines, articles are placed in one end of the machine, passed through the device, and subjected to various operations based on their location in the device.
To conserve significant amounts of water and other resources in such systems, they often reuse wash water and the detergents contained therein during a wash cycle. Fresh water is imported to the device during a rinse cycle to remove soap and other remnants of a wash cycle from articles in the warewashing machine. This rinse water then supplements the previously used wash water, and a portion of the previously used wash water is removed from the machine. Accordingly, such systems continuously import fresh water to prevent problems associated with excessive reuse of the wash water.
While meeting with substantial success, such systems have also met with certain limitations. Importantly, the addition of rinse water to the wash water results in dilution of the detergent and other desirable materials in the wash water. Further, the amount (or "charge") of detergent or other material that is added after each rinse cycle varies substantially from the amount that is to be added when a warewasher is initially started.
In the past, a variety of solutions have been proposed to the above problems. Commonly, such devices use of various chemical sensors such as conductivity probes. When the concentration of the wash water reaches predetermined limits, such devices then dispense additional detergent. Such systems have the disadvantage of requiring expensive, high maintenance chemical probes, which are prone to failure particularly in hard water operation.
Certain control systems for warewashing machines base detergent charge timing on the status of the machine. For example, certain control systems have dispensed materials when the device is in a rinse cycle. However, such devices have also met with certain limitations. For example, the devices tend to be complex to install as a result of the many electrical interfaces with the warewashing device. Further, such control systems are prone to difficulty when the power to the warewashing machine is cut-off since the device does not "recall" when the last detergent charge has taken place. Such devices have experienced further difficulty because they tend to be failure prone, complex to set-up, and the like.
From the above it is seen that an improved control system for warewashing equipment and systems, is needed.